1. Field of the Invention
This invention relates to vessels of the type having a discharge orifice therein and, more particularly, to a stopper system that allows the orifice to be selectively blocked.
2. Background Art
There are a multitude of different vessels having a discharge orifice which is required to be selectively opened and blocked. In some environments, a relatively simple valve structure can be utilized to accomplish this. However, the discharge of high temperature, pourable material may require a substantially different structure.
Relatively complicated valve mechanisms have been devised for molten metal vessels. These valves commonly utilize replaceable refractory elements. Operation of the valve may occur by relatively sliding refractory plates to selectively register openings therethrough.
While this type of refractory valve has proven effective in operation, it has a number of drawbacks. First of all, the refractory plates are prone to wearing after continued use as a result of which pouring characteristics may be changed and seals may be compromised.
In the event that replacement of paits in such a valve is required, the disassembly required to effect this replacement may be quite extensive and time consuming. This may result in significant down time.
A cruder method of controlling the state of vessel orifice involves the use of sand. Sand may be mounded at the orifice to prevent the discharge of molten metal or slag. When it is required to open the orifice, the sand is redistributed to expose the orifice.
When this operation is performed manually, it may be time consuming and fatiguing. Further, the operator of the valve is required to be positioned in close proximity to the high temperature vessel, thereby risking exposure to high temperatures and in a worse case the discharge of material.
Another option in the prior art for sealing a vessel orifice is to solidify the discharging material at the orifice. This can be done by cooling the region around the orifice. When it is desired to initiate flow through the orifice, the solidified material can be heated to a liquid state, thereby allowing flow out through the orifice.
Another available option is to utilize a stopper element which is loosely inserted into the orifice. The material in the vessel is allowed to flow around the stopper material and solidified to create a complete seal. When it is desired to release the material from the vessel, the stopper element is heated to melt the solidified material and allow the stopper to be removed to achieve a flow condition.